Hawaii Five-0 is packing in the guest stars for "Ua' aihue."

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Filming as episode 11 (airing order unconfirmed), the upcoming episode will feature White Collar's Willie Garson and Lost's Rebecca Mader.

Currently staring as the Wicked Witch in Once Upon A Time, Mader took a quick break from the rainy Vancouver set to warm up with the cast of Hawaii Five-0 in mid-October.

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"Guess why I'm in Hawaii?!" Mader teased before reuniting with two of her old Lost co-stars on set. "Did I mention Im REALLY EXCITED to be with my boys [Daniel Dae Kim (Chin)] & [Jorge Garcia (Jerry)] again? I was lost but now I'm found."

Directed by Jeffrey Hunt ("Makani 'Olu a Holo Malie," "Hoku Welowelo"), "Ua' aihue" may have something to do with a piece of artwork. Hunt posted a photo from set that appears to place the team at an upscale art show (see photos above).

Find out more when Hawaii Five-0 airs Fridays at 9 p.m. ET. Click the video below to see a preview for the series' upcoming Halloween-themed episode, "Ho'oma'ika."